The invention relates to an apparatus and a method for the detection of an object moving in the monitoring range of a camera.
A reference image with an object-free monitored region is usually recorded and stored with such methods or apparatuses. Images of the monitored region are then continuously recorded and compared with the stored reference image during the actually occurring monitoring. If deviations result here, the presence of an object is assumed and a corresponding reaction triggered, for example a switching off of a machine. The comparison of the recorded images with the stored reference image takes place, for example, in such a way that the brightness of pixels of the reference image and of the actually recorded image which mutually correspond with respect to their spatial position are compared to one another and then a reaction is triggered if the determined brightness of a specific number of pixels of the actually recorded image does not agree with the corresponding brightness values of the pixels of the reference image.
A problem in the use of known apparatuses and known methods of this kind is the fact that the camera and/or parts of the monitored region can move, for example as a consequence of permissible vibrations or oscillations, which can then result in changes in the images recorded and, with an object-free monitored region, in an unwanted triggering of reactions. Being more specific, it is for example possible for a hazardous region of a machine to be monitored using the camera with the intention being to switch off the machine whenever a person moves into the monitored region. Such a person causes brightness differences in the images recorded during the monitoring with respect to an object-free reference image so that when persons intrude into the monitored region, a stopping of the machine can take place in a desired manner. If, however, a vehicle now drives past the monitored machine, for example, and produces vibrations which move either the camera or the machine slightly, an—unwanted—stopping of the machine will also take place in this case due to the differences between the images recorded and the reference image, even though no person is located in the monitored region.